1. Field of the Invention
This invention pertains to the field of cockpit indicators or display units that provide terrain information to pilot or flight crew of an aircraft.
2. Description of the Related Art
Beginning in the early 1970's, a number of studies looked at the occurrence of “controlled flight into terrain” (CFIT)-type accidents, where a properly functioning airplane under the control of a fully qualified and certificated crew is flown into terrain (or water or obstacles) with no apparent awareness on the part of the crew. Findings from these studies indicated that many such accidents could have been avoided if a warning device called a ground proximity warning system (“GPWS”) was used. There have been numerous patents issued in the field of GPWS and related art. A sampling of patents issued in the art and related art include U.S. Pat. Nos. 5,839,080; 6,092,009; 6,122,570; 6,138,060; 6,219,592; and 7,145,501.
Advances in technology have permitted vendors and designers of avionics equipment to develop newer type of GPWS that provides greater situational awareness for flight crews. The U.S. Federal Aviation Administration (“FAA”) has classified such systems as Terrain Awareness and Warning Systems (“TAWS”). The advancement of technologies—more precise navigation systems, increased computer memory storage, and better display technology—have allowed further development of in the common features of TAWS: (1) use of airplane position information from the aircraft's navigation system(s), (2) an onboard terrain database, and (3) a means of displaying the surrounding terrain. Aircraft position information from the aircraft's navigation system is fed to a TAWS computer. The TAWS computer compares the airplane's current position and flight path with the terrain database associated with the system. If there is a potential threat of collision with terrain, the TAWS computer sends warning alerts to the airplane's audio system.
Manufactures have produced cockpit indicators for presenting terrain information to the pilot. For instance terrain information may be depicted in three colors (e.g., red, yellow, and green) and variable density dot patterns. Each of the colors and patterns, such as those discussed in U.S. Pat. No. 6,122,570, could indicate a different level of terrain threat in front of the aircraft. For example, a high density dot pattern that could be associated with a first level of terrain threat may be defined as a function of the altitude. A high density dot pattern could be associated with a color such as red, a color traditionally associated with a warning alert of TAWS. Likewise, medium and low density dot patterns that could be associated with second and third levels of terrain threat, respectively, may be defined as a function of the altitude. Medium and low density dot patterns could be associated with different colors such as amber and green, where amber is a color traditionally associated with a caution alert of TAWS.
Although these traditional terrain indicators present terrain information to a pilot, they tend to obscure or clutter the presentation of information that may interfere with other functions display on the indicator. In addition, other systems share the same colors as used in terrain indicating systems. For example, a weather radar system may also use the colors red and yellow in depicting weather information. If so, then a pilot may be limited to viewing either weather or terrain information at one time and not both simultaneously. The embodiments disclosed herein present novel and non-trivial system and method for presenting an image of terrain on a display unit of an aircraft.